Re: [PATCH 1/2] drm/core: Reuse the reserved member in drm_event_vblank for crtc_id.

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Aug 10, 2016 at 12:46:23PM +0200, Maarten Lankhorst wrote:
> When doing a atomic commit affecting multiple crtc's, multiple events
> are generated. The user_data member does not allow you to distinguish,
> because they all have the same pointer.
> 
> I've chosen to use crtc_id, because using pipe would create ambiguity
> when pipe = 0. A test for != 0 is easier to implement, and crtc_id
> will never be 0.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Stone <daniels@collabora.com>
> ---
>  drivers/gpu/drm/drm_irq.c | 2 ++
>  include/uapi/drm/drm.h    | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 97c70642dbe1..f01bb0eea31c 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -1021,6 +1021,7 @@ void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
>  
>  	e->pipe = pipe;
>  	e->event.sequence = drm_vblank_count(dev, pipe);
> +	e->event.crtc_id = crtc->base.id;
>  	list_add_tail(&e->base.link, &dev->vblank_event_list);
>  }
>  EXPORT_SYMBOL(drm_crtc_arm_vblank_event);
> @@ -1048,6 +1049,7 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
>  		now = get_drm_timestamp();
>  	}
>  	e->pipe = pipe;
> +	e->event.crtc_id = crtc->base.id;
>  	send_vblank_event(dev, e, seq, &now);
>  }
>  EXPORT_SYMBOL(drm_crtc_send_vblank_event);
> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
> index 452675fb55d9..dced4d4517d6 100644
> --- a/include/uapi/drm/drm.h
> +++ b/include/uapi/drm/drm.h
> @@ -850,7 +850,7 @@ struct drm_event_vblank {
>  	__u32 tv_sec;
>  	__u32 tv_usec;
>  	__u32 sequence;
> -	__u32 reserved;
> +	__u32 crtc_id; /* 0 on older kernels that do not support this */

Same comment as in reply to Michel's patch: Is there really no existing
userspace which would fail to compile now because we renamed this? Simply
creating a new drm_event_vblank2 struct would fix that.
-Daniel

>  };
>  
>  /* typedef area */
> -- 
> 2.7.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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